The contribution of off-shell gluons to the longitudinal structure function F_L

We present results for the structure function F_L for a gluon target having nonzero transverse momentum square at order \alpha_s. The results of double convolution (with respect to Bjorken variable x and the transverse momentum) of the perturbative part and the unintegrated gluon densities are compared with recent experimental data for F_L at low x values and with predictions of other approaches.